The square inch (in²) is a small imperial area unit equal to a square measuring one inch on each side, commonly used in engineering specifications, screen size descriptions, and pressure measurements. Piston areas, material stress calculations, and electronic component sizes are frequently expressed in square inches. One square inch equals exactly 6.4516 square centimeters.

The square mile (mi²) is a large imperial area unit equal to 640 acres or about 2.59 square kilometers, used for measuring expansive territories like cities, counties, and national parks. Geographic data in the United States and United Kingdom frequently references square miles when describing regions, especially in population density calculations. One square mile equals exactly 2.58999 square kilometers.